142 publications from this institution
Glacial landforms are abundant in the North Sea basin and are often used to reconstruct the impact and dynamics of ice sheets during the Pleistocene. Geophysical methods have allowed the mapping and structural analysis of glacial landforms at the surface and in the subsurface to estimate the position of former ice margins in the North Sea. However, the glacial history of the southeastern North Sea remains underexplored. In this study, we present a structural analysis of Late Pliocene to Late Pleistocene sediments based on a dense grid of 2D high‐resolution multi‐channel reflection seismic data from the German sector of the southeastern North Sea. We show that the Heligoland Glacitectonic Complex (HGC) is larger than previously assumed (700 km 2 , 32×22 km) and characterized by three distinct zones of thrusting and deformation on two décollements. The kinematic restoration of seismic cross‐sections and dip measurements of thrust faults demonstrate that the HGC was formed by an ice lobe advancing from the southeast. To explain the origin of the HGC, we provide alternative models for its formation during a single ice advance or two ice advances in the study area. Furthermore, we validate the early or pre‐Elsterian age of the HGC based on nearby Elsterian tunnel valleys, and conclude that salt structures in the subsurface may have influenced its location.
Aquino da Silva, A.G.; Stattegger, K.; Schwarzer, K.; Vital, H., and Heise, B., 2015. The influence of climatic variations on river delta hydrodynamics and morphodynamics in the Parnaíba Delta, Brazil.In this work, we present a baseline study on the geo-environmental, morphodynamical, and hydrodynamical conditions of the Parnaíba River and its mouth, the Parnaíba River Delta (PRD). The outline of the PRD indicates that waves are the major forcing factor for delta development. Furthermore, the shape of the delta suggests that there is a considerable degree of asymmetry in its formation. The asymmetry is the result of coastal current influence on the reworking of the sediments that are discharged by the river. To investigate the hydrodynamic conditions of the area, field measurements were conducted on the river, offshore of the PRD, and on the tidal channels of the west part of the delta. At these locations, the currents, salinity, temperature, and tidal dynamics were measured. In addition, a time series of rainfall, river discharge, and suspended sediment concentration (SSC) were obtained from Brazilian governmental agencies. The interpretation of all of the data was used to determine how they interact to characterize the hydro- and morphodynamics of the PRD. Harmonic analysis was of high importance in the analysis of the time series, and it was employed to identify longer periods presenting similarities in terms of meteorological conditions. This allowed determination of the interconnection between rainfall, river discharge, and SSC with the occurrence and intensity of the El Niño-Southern Oscillation. The influence of river discharge, rainfall, and SSC on shoreline change was demonstrated through the analysis of decadal shoreline evolution using a series of LANDSAT images covering the period from 1981 to 2009. The analysis revealed that most changes occurred westward from the PR mouth. Changes in spit migration velocity were correlated to variations in riverine sediment yielded as a result of variations of river discharge and SSC.
No abstract is provided for this article.
Habitats are defined as “areas of the seabed that are (geo)- statistically significantly different from their surroundings in terms of physical, chemical and biological characteristics, when observed at particular spatial and temporal scales” [1].
Pebbles, cobbles, and boulders are commonly found on abrasion platforms of retreating soft rock cliff-coasts, which are widespread along the southwestern Baltic Sea coast. So far, little has been known about the behavior of these residual sediments under the influence of wave impact. Thus, detailed field measurements were carried out at three different coastal stretches of the southwestern Baltic Sea between 1997 and 1999. Underwater photo stations were established and marked pebbles and cobbles (tracer) were placed on the seafloor. During an 18-month period, these stations were revisited up to 10 times, taking reproducible photos of the seafloor and measuring any tracer movement. Local wave data were collected by wave buoys. In water depths of up to 5.6 m and distances from the shoreline of up to 300 in pebbles, cobbles and even boulders were moved by wave action. Displacements were in the range of up to tens of meters, but highly dependent on water depth and wave energy input. Nearly all marked pebbles moved onshore, coinciding with the direction of the main wave propagation. It can be assumed that residual sediments are an important sediment source for the development of beach ridges in the adjacent coastal lowlands. There is evidence that the whole residual sediment layer, even of several centimeters to decimeters in thickness, has been reworked repeatedly. Former assumptions, that residual sediments covering the solid seafloor might protect it from abrasion, seem no longer valid.
No abstract is provided for this article.
Electrical prospecting of soils and rocks is far more diversified than other geophysical methods. Some techniques use natural electrochemically-generated currents, the so called self-potential method. Other techniques make use of electric currents or fields that are introduced into the ground. The resistivity method has been traditionally used for differentiating oil and gas bearing from water saturated rocks. The main scope of this paper is to investigate the applicability of using electrical methods to evaluate some geological and geotechnical parameters of marine sediments concerning engineering and environmental problems.
